Backpacks, specifically those designed to carry large loads (in terms of weight and/or bulk), typically feature two shoulder straps, two load lifter straps, a chest strap, and a hip belt. The hip belt is designed to transfer a substantial amount of the weight of the backpack from rigid or semi-rigid supports of the backpack frame to the hips of the backpack user. Each shoulder strap features a load lifter strap connecting the upper face of the shoulder strap to the backpack frame. The purpose of the load lifter strap is to pull the shoulder strap off the user's shoulders to allow the weight of the backpack to be transferred to the user's hips. The load lifter straps must be affixed to the backpack frame supports above the top of the user's shoulders (ideally two or more inches) in order to adequately lift the shoulder straps off the user's shoulders.
One embodiment relates to the Mystery Ranch, Ltd. NICE Frame, as disclosed in U.S. Pat. No. 7,673,777 to Gleason (2010). The NICE Frame is an external backpack frame comprising three vertical and three horizontal cross support members attached to a fabric membrane. An example of the NICE Frame is shown FIG. 1.
With additional reference to FIG. 2, U.S. Pat. No. 7,673,777 to Gleason (2010) further describes a spade, shown as 340 attached to a NICE Frame, comprising a semi-rigid tongue attached to a packbag or load carrier 341. The spade 340 is configured to fit in a gap between one of the frame's cross support members and the membrane 350, providing stability and assisting in transferring the load of the packbag or load carrier 341 to at least one cross support member.
The NICE Frame is designed to fit a multitude of modular packbags and accessories for load carrying purposes. An adjustable shoulder strap assembly, known as a yoke 310, is coupled with membrane 350, and a hip belt 320 is attached to the lower front of the frame. Yoke 310 is primarily designed to stabilize the backpack load and more properly position portions of the backpack relative to the user's torso and shoulders. Yoke 310 is adjustable to fit the torso length of the user relative to hip belt 320, so that the internal, semi-rigid framesheet 318 terminates near the top of the user's shoulders. Adjusted in this manner, hip belt 320 is positioned to properly transfer the weight carried by the NICE frame to the user's hips.
Yoke 310 can be adjusted so the top of framesheet 318 is above the NICE Frame's support structure. Adjusted in this manner, as is common for users with average and above-average torso lengths, load lifter straps 313 and 314 are no longer affixed to the frame optimally above the user's shoulders and are not capable of lifting the shoulder straps 311 and 312 off the user's shoulders when hip belt 320 is in use. The result is shoulder fatigue and stress on the user's spine from the weight of a loaded packbag on the frame.
The Mystery Ranch NICE 6500 packbag addresses this problem by integrating in the packbag two vertical aluminum stays which extend approximately five inches above the NICE Frame's support members. The lower sections of the aluminum stays are joined by a plastic strip that slides under the NICE Frame's center horizontal support member in the style of the spade described by Gleason, further securing and stabilizing the frame extender on the frame. Because the aluminum stays are an integral part of the packbag, the frame extending function is only provided while the packbag is attached to the NICE frame; thus, a user desiring to attach another packbag to the frame will lose the frame extending benefit of the NICE 6500 packbag. The aluminum stays cannot be removed from the packbag to reduce weight or provide additional head clearance, and damage to the internal frame extender cannot be easily repaired. The inclusion of the internal frame extender increases the complexity and manufacturing cost of the packbag.
The Mystery Ranch Metcalf packbag features an internal frame extender similar to that of the NICE 6500 packbag. It comprises two vertical carbon fiber stays joined by a lower plastic strip to form an internal extender assembly. The internal extender assembly is secured inside the packbag. The lower section of the internal extender assembly slides under the NICE Frame's center horizontal support member in the style of the internal frame extender in the NICE 6500 packbag. While the internal extender assembly can be removed from the Metcalf packbag, it cannot function as a frame extender independently of the packbag. The packbag must be constructed to retain the internal extender assembly and allow the lower section to slide under the NICE Frame's center horizontal support member, increasing the complexity and manufacturing cost of the packbag.
A NICE Frame extending panel developed in 2010 by Robert W. Looney of Bend, Oreg., shown attached to a NICE Frame in FIG. 3, is designed to function independently of a packbag. It comprises a machined aluminum panel 410 featuring numerous slots to retain straps 401 and 402 to attach the extending panel to a NICE Frame. Additional slots are provided to retain straps 403 and 404 to attach the NICE Frame load lifter straps, shown as 313 and 314 in FIG. 11, to the upper portion of the frame extending panel. The frame extending panel is attached to and stabilized on a NICE Frame without the use of a packbag by straps 401 and 402. A packbag can then be attached to the NICE frame with the frame extending panel attached. In spite of these improvements over the NICE 6500 and Metcalf packbags, the frame extending panel suffers from a number of disadvantages:
(a) The heavy, single-piece aluminum panel 410 impedes the designed flexibility of the NICE Frame's support members.
(b) Expensive routing or molding equipment must be used to fabricate panel 410. Additionally, sewn straps 401, 402, 403 and 404 must be provided in order to attach the frame extending panel to a NICE Frame, increasing manufacturing cost and logistical requirements.
(c) Damage rendering panel 410 unserviceable, as may be encountered if the backpack frame is dropped with a heavily loaded packbag, cannot be easily repaired.
(d) Camouflage or other forms of concealment (such as low-visibility colors), as may be required for hunters, military personnel and security forces, must be applied to panel 410 by paint, anodizing, fabric-like wraps or other similar methods, increasing manufacturing time and cost.